同时使用asyncio和Tkinter（或另一个GUI库），而不冻结GUI

Question

我想使用asyncio与tkinterGUI相结合。我是asyncio的新手，对它的理解不是很详细。这里的示例在单击第一个按钮时启动10个任务。这个任务只是在几秒钟内用睡眠（）来模拟工作。

示例代码在Python3.6.4rc1下运行良好。但问题是GUI被冻结了。当我按下第一个按钮并启动10个异步任务时，我不能在GUI中按下第二个按钮，直到所有任务都完成。图形用户界面永远不应该冻结——这是我的目标。

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

from tkinter import *
from tkinter import messagebox
import asyncio
import random

def do_freezed():
    """ Button-Event-Handler to see if a button on GUI works. """
    messagebox.showinfo(message='Tkinter is reacting.')

def do_tasks():
    """ Button-Event-Handler starting the asyncio part. """
    loop = asyncio.get_event_loop()
    try:
        loop.run_until_complete(do_urls())
    finally:
        loop.close()

async def one_url(url):
    """ One task. """
    sec = random.randint(1, 15)
    await asyncio.sleep(sec)
    return 'url: {}\tsec: {}'.format(url, sec)

async def do_urls():
    """ Creating and starting 10 tasks. """
    tasks = [
        one_url(url)
        for url in range(10)
    ]
    completed, pending = await asyncio.wait(tasks)
    results = [task.result() for task in completed]
    print('\n'.join(results))


if __name__ == '__main__':
    root = Tk()

    buttonT = Button(master=root, text='Asyncio Tasks', command=do_tasks)
    buttonT.pack()
    buttonX = Button(master=root, text='Freezed???', command=do_freezed)
    buttonX.pack()

    root.mainloop()

...由于此错误，我无法再次运行该任务。

Exception in Tkinter callback
Traceback (most recent call last):
  File "/usr/lib/python3.6/tkinter/__init__.py", line 1699, in __call__
    return self.func(*args)
  File "./tk_simple.py", line 17, in do_tasks
    loop.run_until_complete(do_urls())
  File "/usr/lib/python3.6/asyncio/base_events.py", line 443, in run_until_complete
    self._check_closed()
  File "/usr/lib/python3.6/asyncio/base_events.py", line 357, in _check_closed
    raise RuntimeError('Event loop is closed')
RuntimeError: Event loop is closed

为什么多线程是一个可能的解决方案？只有两个线程-每个循环都有自己的线程？

编辑：在回顾这个问题和答案之后，它几乎与所有GUI库（例如PygObject/Gtk、wxWidgets、Qt等）都相关。

Answer 1

我参加聚会有点晚了，但如果你不是针对Windows，你可以使用aiotkinter来实现你想要的。我修改了您的代码以向您展示如何使用此软件包：

from tkinter import *
from tkinter import messagebox
import asyncio
import random

import aiotkinter

def do_freezed():
    """ Button-Event-Handler to see if a button on GUI works. """
    messagebox.showinfo(message='Tkinter is reacting.')

def do_tasks():
    task = asyncio.ensure_future(do_urls())
    task.add_done_callback(tasks_done)

def tasks_done(task):
    messagebox.showinfo(message='Tasks done.')

async def one_url(url):
    """ One task. """
    sec = random.randint(1, 15)
    await asyncio.sleep(sec)
    return 'url: {}\tsec: {}'.format(url, sec)

async def do_urls():
    """ Creating and starting 10 tasks. """
    tasks = [
        one_url(url)
        for url in range(10)
    ]
    completed, pending = await asyncio.wait(tasks)
    results = [task.result() for task in completed]
    print('\n'.join(results))

if __name__ == '__main__':
    asyncio.set_event_loop_policy(aiotkinter.TkinterEventLoopPolicy())
    loop = asyncio.get_event_loop()
    root = Tk()
    buttonT = Button(master=root, text='Asyncio Tasks', command=do_tasks)
    buttonT.pack()
    buttonX = Button(master=root, text='Freezed???', command=do_freezed)
    buttonX.pack()
    loop.run_forever()

Answer 2

在对代码稍作修改时，我在主线程中创建了asyncioevent_loop，并将其作为参数传递给asyncio线程。现在，获取网址时，Tkinter不会冻结。

from tkinter import *
from tkinter import messagebox
import asyncio
import threading
import random

def _asyncio_thread(async_loop):
    async_loop.run_until_complete(do_urls())


def do_tasks(async_loop):
    """ Button-Event-Handler starting the asyncio part. """
    threading.Thread(target=_asyncio_thread, args=(async_loop,)).start()

    
async def one_url(url):
    """ One task. """
    sec = random.randint(1, 8)
    await asyncio.sleep(sec)
    return 'url: {}\tsec: {}'.format(url, sec)

async def do_urls():
    """ Creating and starting 10 tasks. """
    tasks = [one_url(url) for url in range(10)]
    completed, pending = await asyncio.wait(tasks)
    results = [task.result() for task in completed]
    print('\n'.join(results))


def do_freezed():
    messagebox.showinfo(message='Tkinter is reacting.')

def main(async_loop):
    root = Tk()
    Button(master=root, text='Asyncio Tasks', command= lambda:do_tasks(async_loop)).pack()
    Button(master=root, text='Freezed???', command=do_freezed).pack()
    root.mainloop()

if __name__ == '__main__':
    async_loop = asyncio.get_event_loop()
    main(async_loop)

Answer 3

试图同时运行两个事件循环是一个可疑的命题。然而，由于root.mainloop只是重复调用root.update，因此可以通过将更新作为异步任务重复调用来模拟主循环。这里有一个这样做的测试程序。我认为向tkinter任务添加asyncio任务会起作用。我检查了它仍然运行3.7.0a2。

"""Proof of concept: integrate tkinter, asyncio and async iterator.

Terry Jan Reedy, 2016 July 25
"""

import asyncio
from random import randrange as rr
import tkinter as tk


class App(tk.Tk):

    def __init__(self, loop, interval=1/120):
        super().__init__()
        self.loop = loop
        self.protocol("WM_DELETE_WINDOW", self.close)
        self.tasks = []
        self.tasks.append(loop.create_task(self.rotator(1/60, 2)))
        self.tasks.append(loop.create_task(self.updater(interval)))

    async def rotator(self, interval, d_per_tick):
        canvas = tk.Canvas(self, height=600, width=600)
        canvas.pack()
        deg = 0
        color = 'black'
        arc = canvas.create_arc(100, 100, 500, 500, style=tk.CHORD,
                                start=0, extent=deg, fill=color)
        while await asyncio.sleep(interval, True):
            deg, color = deg_color(deg, d_per_tick, color)
            canvas.itemconfigure(arc, extent=deg, fill=color)

    async def updater(self, interval):
        while True:
            self.update()
            await asyncio.sleep(interval)

    def close(self):
        for task in self.tasks:
            task.cancel()
        self.loop.stop()
        self.destroy()


def deg_color(deg, d_per_tick, color):
    deg += d_per_tick
    if 360 <= deg:
        deg %= 360
        color = '#%02x%02x%02x' % (rr(0, 256), rr(0, 256), rr(0, 256))
    return deg, color

loop = asyncio.get_event_loop()
app = App(loop)
loop.run_forever()
loop.close()

tk更新开销和时间分辨率都随着时间间隔的减小而增加。对于gui更新，与动画相反，每秒20次就足够了。

我最近成功地运行了异步def协程，包含了tkinter调用，并等待主循环。原型使用异步任务和期货，但我不知道添加普通异步任务是否有效。如果一个人想一起运行asyncio和tkinter任务，我认为用asyncio循环运行tk更新是一个更好的主意。

编辑：至少如上所述，没有异步def协程的异常会杀死协程，但会在某个地方被捕获并丢弃。无声的错误非常令人讨厌。